ADU Rules in Alameda County, California
We track 6 cities in Alameda County. Each city writes its own ADU ordinance on top of California law, so size limits, fees, and design rules differ from one city to the next. Among the cities we track, Oakland has the lowest starting permit fees ($5,000 – $22,000).
Cities
6
Max Detached Size
1,000–1,200 sq ft
Build Costs From
$175,000
Pre-approved Plans
4 of 6 cities
Alameda County Cities Compared
| City | Max detached | Height | Permit fees | Build cost |
|---|---|---|---|---|
| Oakland | 1,000 sq ft | 20 ft for a Category Two detached ADU (zone height limit applies if all regular zone setbacks are met) | $5,000 – $22,000 | $200,000 – $550,000 |
| Fremont | 1,200 sq ft | 16 ft detached (18 ft within 1/2 mile of major transit) | $10,000 – $20,000 | $200,000 – $420,000 |
| Hayward | 1,200 sq ft | 16 ft (detached) | $9,000 – $18,000 | $185,000 – $380,000 |
| Berkeley | 1,200 sq ft | 20 ft (detached new construction) | $12,000 – $25,000 | $230,000 – $450,000 |
| Livermore | 1,200 sq ft | 16 ft | $9,000 – $18,000 | $180,000 – $365,000 |
| San Leandro | 1,200 sq ft | 16 ft (detached) | $9,000 – $18,000 | $175,000 – $360,000 |
Oakland ADU rules
Oakland sorts ADUs into categories under Planning Code Section 17.103.080: Category One converts or rebuilds existing space, while a new detached backyard unit is a Category Two ADU. The city offers pre-approved studio, one-bedroom and two-bedroom plans with lower permit fees, and runs a program to legalize unpermitted ADUs under AB 2533. Hillside lots face extra fire safety, access and geotechnical review.
Fremont ADU rules
Fremont caps new attached ADUs at 1,000 sq ft and detached ADUs at 1,200 sq ft, under rules the City Council updated in 2023. Attached ADUs can reach 30 ft and two stories where the zone allows, which is more generous than the state minimum. The city publishes preapproved ADU plans, and each ADU needs its own permit even when built alongside other work on the house.
Hayward ADU rules
Hayward limits detached ADUs to 1,200 sq ft and 16 ft, with attached units capped at 50% of the main home or 1,200 sq ft. The city keeps an online ADU Plans Gallery of pre-approved designs from private architects, which homeowners buy directly and pair with site-specific drawings. Hillside parcels in the east of the city may need geotechnical review.
Berkeley ADU rules
Berkeley allows new detached ADUs up to 20 ft tall, taller than the state minimum, and up to 1,200 sq ft outside the Hillside Overlay District. Inside the Hillside Overlay, size drops to 850 sq ft for a studio or one bedroom and 1,000 sq ft for two or more bedrooms, and fire-safety and access rules adopted after the 2021 public-safety amendments apply. Setbacks are 4 ft on the sides and rear, with the front setback set by the underlying zone.
Livermore ADU rules
Livermore allows detached ADUs up to 1,200 sq ft with 4 ft side and rear setbacks and at least 16 ft of height. Pre-approved plans can be used citywide with faster plan review and lower permit costs, but you must contract with the plan's designer and still provide site-specific drawings. New attached or detached ADUs may need a parking space unless the lot qualifies for an exemption.
San Leandro ADU rules
San Leandro waived Park Impact Fees and street improvement fees for all ADUs in July 2025, regardless of size. Detached ADUs can reach 1,200 sq ft where 50% of the main house allows it, and 18 ft within half a mile of BART or another major transit stop. The city points homeowners to the Alameda County ADU Resource Center for step-by-step help.
Rules that apply in every California city are summarized in our California ADU law guide. See all California cities or compare every city side by side.